Variable-speed, two-stage and single-stage heat pumps compared
Among the 936 rated split systems, variable-speed units keep a median 83% of their 47°F heating capacity at 5°F, against 55% for two-stage and 52% for single-stage units. None of the 146 single-stage split systems carries the EPA cold-climate designation; 60 two-stage units do.
What the staging field records
The ENERGY STAR list records how each outdoor unit's compressor runs: in one stage, in two stages, or continuously variable, which this site calls variable-speed. The field describes the hardware; it says nothing about how a system is controlled once installed. All 1,604 rated mini- and multi-splits in the list are variable-speed, so the comparison below is about split systems, with single-package units added at the end.
Split systems, stage by stage
Variable-speed units make up 642 of the 936 rated split systems, with 148 two-stage and 146 single-stage units. On the seasonal ratings the two fixed-stage groups look alike: both have a median HSPF2 of 8.1 and a median SEER2 of 16. Variable-speed units are higher on both, at 9.4 and 18.
| Compressor | Rated split systems | Median HSPF2 | Median SEER2 | Median kept at 5°F | Median COP at 5°F | EPA cold-climate designation |
|---|---|---|---|---|---|---|
| Single-stage | 146 | 8.1 | 16 | 52% | 2.20 | 0 (0%) |
| Two-stage | 148 | 8.1 | 16 | 55% | 2.21 | 60 (41%) |
| Variable-speed | 642 | 9.4 | 18 | 83% | 2.00 | 555 (86%) |
The cold-weather figures separate the groups far more clearly. Variable-speed split systems keep a median 83% of their 47°F capacity at 5°F. Two-stage units keep 55% and single-stage units 52%. The designation follows the same pattern: 86% of variable-speed units carry it, 41% of two-stage units and none of the single-stage units.
Staging by size class
The mix of compressors is not the same in every split-system class. Variable-speed units make up 75% of the 2-ton class but only 18% of the 3.5-ton class. That class also has the lowest median share kept at 5°F of all split-system classes, so a class median always reflects its compressor mix as much as anything else. The split-system overview lists every class with its share of variable-speed units.
Who reaches the top of the HSPF2 table
Of the 93 split systems with the highest HSPF2, 91 are variable-speed, 2 two-stage and 0 single-stage. Fixed-stage units are not absent from the top of the seasonal heating table, but they are rare there, while they make up 31% of all rated split systems.
Two-stage units with the designation
The 60 two-stage split systems with the EPA cold-climate designation keep a median 60% of their 47°F capacity at 5°F, against 53% for the other two-stage units. Most of them list less than 70% at 5°F in their designated matches; their product listings carry the designation as EPA publishes it, and this site shows the listed ratio next to it. The brands with the most designated two-stage products are Fujitsu (12), Trane (12), and Rheem (9).
The COP surprise
One figure runs the other way. The median COP at 5°F is 2.20 for single-stage and 2.21 for two-stage split systems, against 2.00 for variable-speed units. The list does not say why. What it does show is that COP at 5°F and the share of heat kept at 5°F are separate measures: a fixed-stage unit can list an efficient but small output at 5°F, while a variable-speed unit lists more heat at a slightly lower COP. The cold finder can filter on both at once.
Single-package units
The 73 single-package heat pumps split into 41 two-stage and 32 variable-speed units. The contrast is sharper still: 31 of the variable-speed units carry the cold-climate designation and none of the two-stage units does. Their median shares kept at 5°F are 73% and 46%.
In the finder
The finder's default list shows 3-ton split systems with the designation that keep at least 70% of their 47°F capacity at 5°F. Of the 137 products in it, 130 are variable-speed and 7 two-stage. Switching the compressor filter changes the list at once, and the address of the page records the choice.
What this does and does not tell
The staging field is a reliable sorting key in this list: on split systems it predicts the 5°F figures better than any brand name or refrigerant does. It is still a summary. Inside each group the spread is wide, and some two-stage units list more heat at 5°F than many variable-speed ones. The split-system size classes show every unit against its own class, and the finder's compressor filter narrows any list to one staging type.
All figures are listed ratings of certified matched systems, certified as of October 27, 2026. They are not a recommendation for any type of equipment.
Sources
- U.S. EPA, ENERGY STAR Certified Heat Pumps (data.energystar.gov, dataset 83eb-xbyy), certified as of 2026-10-27.
- Rating families, ratios, medians, ranks and class bands computed by heatpumpratings.online; see How the ratings are read.